U.S. tax authorities have awarded $104 million (64.8 million pounds) to a whistleblower in a major tax fraud case against Swiss bank UBS AG that widened a government crackdown on Americans avoiding taxes in Switzerland, his lawyers said on Tuesday.

Bradley Birkenfeld, freed last month from prison, was not present at the news conference where his attorneys announced the reward made under an Internal Revenue Service whistleblower program that has come in for some criticism in Congress.

Birkenfeld had sought a large payout for his role in a tax-dodging case that resulted in early 2009 in UBS entering into a deferred prosecution agreement and paying $780 million in fines, penalties, interest and restitution.

(Reporting by Patrick Temple-West; Editing by Kevin Drawbaugh and Gerald E. McCormick)